Rechargeable battery power supply overcharge protection circuit

Abstract

A rechargeable power supply overcharge protection circuit is provided with shunt circuits that shunt current about a battery or battery cell (15, 16 and 17) of a string of battery cells when it is charged to a maximum charge limit. The shunt circuit includes shunt regulators (20) connected across each battery cell.

We claim: 
     
       1. A rechargeable power supply comprising a rechargeable battery and means for protecting said battery from being excessively charged during a recharge mode of operation, and with said battery protecting means comprising a voltage divider connected across said battery, and a shunt circuit connected across said battery that includes a shunt regulator operatively coupled with said voltage divider, a second rechargeable battery connected in series with said rechargeable battery, a second voltage divider connected across said second rechargeable battery, and a second shunt circuit connected across said second rechargeable battery that includes a second shunt regulator operatively coupled with said second voltage divider, said second shunt circuit is also connected in series circuit with said first shunt circuit, a current bypass circuit and means for coupling said current bypass circuit across said first and second voltage dividers in response to said first and second rechargeable batteries both being recharged to said preselected fully charged potentials, whereby upon said battery or said second battery being charged to a preselected potential, current is shunted about the charged battery through the shunt circuit coupled thereto. 
     
     
       2. A rechargeable power supply comprising a string of rechargeable batteries having a plurality of rechargeable batteries connected in series circuit a plurality of battery shunt regulators with each battery shunt regulator connected across a different one of said rechargeable batteries, a bypass circuit connectable across said battery string that includes a shunt regulator having its reference voltage terminal operatively coupled with said battery string for connecting said bypass circuit across said battery string upon said battery string being charged to a preselected fully charged potential, and a bypass voltage divider connected across said battery string and wherein said bypass circuit shunt regulator is connected to said bypass voltage divider. 
     
     
       3. The rechargeable power supply of claim 2 wherein said plurality of battery shunt regulators is connected in series circuit to provide a string of battery shunt regulators, and wherein said string of battery shunt regulators is connected across both said battery string and said bypass circuit. 
     
     
       4. A method of charging or recharging a string of rechargeable batteries which comprises the steps of passing current through each battery until each battery reaches its fully charged state, independently shunting recharge current around each fully charged battery by operation of a shunt regulator, and shunting the recharge current around the battery string once all of the batteries are fully charged by operation of another shunt regulator. 
     
     
       5. The method of claim 4 wherein recharge current is independently shunted around each fully charged battery through a circuit, and where recharging current is shunted around the battery string through a circuit.